LM3556 datasheet(15/31 Pages) TI1

15 / 31 page

SDA

Start Condition

Stop Condition

SCL

SDA

data

change

allowed

data

valid

data

change

allowed

data

valid

data

change

allowed

LM3556

www.ti.com

SNVS796C – AUGUST 2011 – REVISED APRIL 2013

LED and/or VOUT Fault

The LED Fault flag in the Flags Register (0x0B) reads back a '1' if the part is active in Flash Mode or Torch

Mode, and the LED output or the VOUT node experiences short condition. The LM3556 determines an LED open

condition if the OVP threshold is crossed at the OUT pin while the device is in Flash Mode or Torch Mode. An

LED short condition is determined if the voltage at LED goes below 500 mV (typ.) while the device is in either

Torch or Flash Mode. There is a delay of 256

μs deglitch time before the LED flag is valid, and 2.048 ms before

the VOUT flag is valid. This delay is the time between when the Flash or Torch current is triggered and when the

LED voltage and the output voltage are sampled. The LED flag can only be reset to '0' by removing power to the

LM3556, or by reading back the Flags Register (0x0B). The mode bits in the Enable Register (0x0A) are cleared

upon an LED and/or VOUT fault.

2C-COMPATIBLE INTERFACE

Data Validity

The data on SDA line must be stable during the HIGH period of the clock signal (SCL). In other words, state of

the data line can only be changed when SCL is LOW.

Figure 31. Data Validity Diagram

A pullup resistor between the controller's VIO line and SDA must be greater than [(VIO-VOL) / 3mA] to meet the

VOL requirement on SDA. Using a larger pullup resistor results in lower switching current with slower edges, while

using a smaller pullup results in higher switching currents with faster edges.

Start and Stop Conditions

START and STOP conditions classify the beginning and the end of the I2C session. A START condition is

defined as the SDA signal transitioning from HIGH to LOW while SCL line is HIGH. A STOP condition is defined

as the SDA transitioning from LOW to HIGH while SCL is HIGH. The I2C master always generates START and

STOP conditions. The I2C bus is considered to be busy after a START condition and free after a STOP condition.

During data transmission, the I2C master can generate repeated START conditions. First START and repeated

START conditions are equivalent, function-wise.

Figure 32. Start and Stop Conditions

Transferring Data

Every byte put on the SDA line must be eight bits long, with the most significant bit (MSB) transferred first. Each

byte of data has to be followed by an acknowledge bit. The acknowledge related clock pulse is generated by the

master. The master releases the SDA line (HIGH) during the acknowledge clock pulse. The LM3556 pulls down

the SDA line during the 9th clock pulse, signifying an acknowledge. The LM3556 generates an acknowledge

after each byte is received. There is no acknowledge created after data is read from the LM3556.

Submit Documentation Feedback

Product Folder Links: LM3556

LM3556 Datasheet(PDF) 15 Page - Texas Instruments

LM3556 Datasheet(HTML) 15 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

Datasheet Download

Link URL